Tire Size Calculator interactive tool
1Current / Factory Tire
2New / Target Tire
What Is Tire Size?
A tire size calculator helps automotive enthusiasts, mechanics, and everyday drivers decode complex metric tire designations. This wheel size calculator is primarily used when someone wants to change the size of their wheels or tires without negatively impacting their vehicle's performance or safety.
How to Read a Metric Tire Size
Look at the sidewall of your tire. You will see a sequence similar to 225/65R17.
- 225 (Section Width): The width of the tire from sidewall to sidewall, measured in millimeters.
- 65 (Aspect Ratio): The height of the tire's sidewall, expressed as a percentage of the width. In this case, the sidewall height is 65% of 225mm.
- R (Construction): Stands for Radial construction (the industry standard).
- 17 (Wheel Diameter): The size of the wheel (rim) the tire is designed to fit, measured in inches.
The Danger of Changing Tire Sizes: Will These Tires Fit My Car?
Your vehicle's computer systems—including the speedometer, odometer, anti-lock brakes (ABS), and traction control—are all calibrated to the factory tire's overall circumference.
If you install larger tires, your vehicle will travel further with every revolution of the wheel. This means your speedometer will read 60 MPH, but you might actually be traveling 65 MPH, risking a speeding ticket. This tire comparison calculator reveals the exact dimensional differences so you can stay within a safe 3% variance from the factory specifications. Always consult with a professional when changing tire sizes significantly.
How To Use the Tire Size Calculator
- Enter the current tire width (e.g., 225), aspect ratio (e.g., 65), and wheel diameter (e.g., 17) in the 'Current Tire' section.
- Review the exact tire dimensions translated into inches (overall diameter, section width, circumference).
- If comparing two tires, enter the second size in the 'New Tire' section to see the difference in speedometer readings and clearance.
- Use the tire comparison calculator feature to ensure any new tire size is within a safe 3% variance of your original size.